Ghost particle that crashed in Antarctica dates back to a star ripped apart by a black hole


A star that breaks into pieces after approaching a black hole. Scientists have detected a neutrino, the “ghost particle”, from such an event for the first time.

DESY, scientific communication laboratory

On October 1, 2019, Earth was hit by an invisible, high-energy cosmic bullet that was moving almost at the speed of light. Trillions of these intergalactic bullets pass through our bodies every second without us knowing, so there is no great concern for the planet, but this particular projectile was special. At the bottom of the world, the ghostly particle came to an end after colliding with an ice molecule. Fortunately, it did so right next to an extremely sensitive detector embedded under the South Pole.

The detection triggered an intergalactic search for the celestial gunman. What had fired the bullet?

In new research, published in the journal Nature Astronomy on Monday, scientists detail the detection of a subatomic particle, known as a neutrino, at the IceCube Neutrino Observatory in Antarctica. Using data from the Zwicky Transient Facility at California’s Palomar Observatory, the researchers were able to trace the origins of the subatomic bullet to an extreme event some 700 million years ago: the cataclysmic destruction of a star when it was smashed by a dungeon.

It is the first time that an event of this type has been related to the detection of neutrinos.

Neutrinos are often described as “ghost particles” because they have no electrical charge and very small masses. Like light, they basically travel in a straight line from their destination. Other charged particles are at the mercy of magnetic fields, but neutrinos simply traverse the cosmos unimpeded. We know that they leave the core of the sun in large quantities, and on Earth we can create them in nuclear reactors and particle accelerators.

In April 2019, the Zwicky facility detected a bright glow around a black hole some 700 million light-years away. The flash of light occurred when a star traveled too close to the black hole, which is around 30 million times more massive than the sun. The immense gravity of the black hole stretched the star and finally I was spaghetti, shattered by extreme forces. This is known as a “tidal disruption event” or TDE.

The star’s violent end is a bright beginning for astronomers. They were able to link the TDE to the IceCube’s detection of the neutrino. The researchers theorize that the TDE spewed about half of the shattered star into space, while the rest settled around the black hole in a gigantic “accretion disk” of hot, glowing dust, gas and debris. The wild energies around the black hole in the disk result in huge jets of matter shooting out of the system. These jets can last for hundreds of days and could account for the short time lag between seeing the TDE and detecting the neutrino in the IceCube.

Astrophysicists reason that this shows the existence of a “central engine” that operates as a natural particle accelerator and can create high-energy neutrinos, some of which can collide with Earth.

“The neutrino emerged relatively late, half a year after the star party started,” said Walter Winter, a theoretical astrophysicist at the German Electron Synchrotron, or DESY. “Our model explains this moment naturally.”

Winter and co-author Cecilia Lunardini published their model in the same issue of Nature Astronomy on Monday.

This is what the accretion disk looks like around a supermassive black hole. The jets flow from the central black hole. The light at the top of the black hole is actually from the opposite side of the hole: the black hole bends space-time so that it appears to be surrounded by light.

DESY, scientific communication laboratory

The discovery of a neutrino emanating from a TDE is a breakthrough for astronomers who hope to understand the universe in new ways. Scientists have only been able trace a neutrino to its origin once before. It was IceCube who also made that detection. In 2017, observatory researchers detected the telltale signature of a neutrino and alerted astronomers to the phenomenon. The telescopes were able to trace the source of the neutrino to a distant galaxy that was home to a “blazar,” a huge black hole surrounded by an accretion disk with a directed jet. directly in the observer.

Both detections show that black holes are intergalactic gunmen, shooting ghost particles from deep space across the universe. This could help astronomers understand the processes that occur near a black hole and could even begin to solve a mystery that has plagued astrophysics since the 1960s: where do the ultra-high energy cosmic rays come from that sometimes crash into Earth’s atmosphere?

Researchers have detected a number of TDEs since the Zwicky Transient Facility began surveying the skies, and in the future, more sensitive telescopes could further link these high-energy particles to events. IceCube will also be essential to improve our understanding. The observatory is expected to be updated during the 2022 and 2023 Antarctic seasons, despite the pandemic, which should increase the number of neutrino detections by a factor of 10.

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